$V=-12 \sin(3t)$ When you differentiate and equate it to $0$, you get $t=\pi/6$, but the speed at this time is $-12$, is this correct? My book has the answer positive $12$. The whole question is: A particle p moves in a straight line such that its displacement from a fixed point $0$ seconds after passing o is given by: $4\cos(3t)-4$
Asked
Active
Viewed 51 times
0
-
Speed vs Velocity – Mauro ALLEGRANZA Feb 27 '20 at 12:34
-
$t=\frac\pi6$ is not the only solution ! And by checking the second derivative, you can tell a minimum from a maximum. – Feb 27 '20 at 12:40
1 Answers
1
Speed is the unsigned magnitude of velocity, so just take the absolute value (drop the negative sign).
Just to add, you don't even have to differentiate the velocity function. $\sin 3t$ has a maximum magnitude of $1$, a fact you should be able to assume without calculus.
Deepak
- 26,801